using System.IO.Compression;
using System.Text;
using System.Text.Json;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;
using NSubstitute;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Transport;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Transport;
using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase;
using ZB.MOM.WW.ScadaBridge.TemplateEngine.Validation;
using ZB.MOM.WW.ScadaBridge.Transport.Encryption;
using ZB.MOM.WW.ScadaBridge.Transport.Import;
using ZB.MOM.WW.ScadaBridge.Transport.Serialization;
using ZB.MOM.WW.ScadaBridge.Transport.Signing;

namespace ZB.MOM.WW.ScadaBridge.Transport.Tests.Signing;

/// <summary>
/// ScadaBridge#45: <see cref="BundleImporter.LoadAsync"/> enforces the signature policy on a
/// real packed bundle, and a signed bundle stays readable by the pre-signing read path.
/// </summary>
public sealed class SignedBundleLoadTests
{
    private const string Passphrase = "correct horse battery";

    private static BundleContentDto Content() => new(
        TemplateFolders: Array.Empty<TemplateFolderDto>(),
        Templates: new[]
        {
            new TemplateDto("Pump", null, null, "signed",
                Array.Empty<TemplateAttributeDto>(), Array.Empty<TemplateAlarmDto>(),
                Array.Empty<TemplateScriptDto>(), Array.Empty<TemplateCompositionDto>()),
        },
        SharedScripts: Array.Empty<SharedScriptDto>(),
        ExternalSystems: Array.Empty<ExternalSystemDto>(),
        DatabaseConnections: Array.Empty<DatabaseConnectionDto>(),
        NotificationLists: Array.Empty<NotificationListDto>(),
        SmtpConfigs: Array.Empty<SmtpConfigDto>(),
        ApiMethods: Array.Empty<ApiMethodDto>());

    private static byte[] Pack(TransportOptions exporterOptions, string? passphrase)
    {
        var serializer = new BundleSerializer();
        var content = Content();
        var contentBytes = serializer.SerializeContentBytes(content);
        var seed = passphrase is null
            ? null
            : new EncryptionMetadata("AES-256-GCM", "PBKDF2-SHA256", 100_000, string.Empty, string.Empty);
        var manifest = new ManifestBuilder().Build("dev", "alice", "1.0.0", seed,
            new BundleSummary(1, 0, 0, 0, 0, 0, 0, 0), Array.Empty<ManifestContentEntry>(), contentBytes);
        var signer = BundleSignerTests.Signer(exporterOptions);
        using var zip = serializer.PackContentBytes(contentBytes, manifest, passphrase,
            new BundleSecretEncryptor(), signer.Sign);
        using var ms = new MemoryStream();
        zip.CopyTo(ms);
        return ms.ToArray();
    }

    private static BundleImporter Importer(TransportOptions opts)
    {
        var iOpts = Options.Create(opts);
        return new BundleImporter(
            bundleSerializer: new BundleSerializer(),
            manifestValidator: new ManifestValidator(),
            encryptor: new BundleSecretEncryptor(),
            entitySerializer: new EntitySerializer(),
            sessionStore: new BundleSessionStore(iOpts, TimeProvider.System),
            unlockRateLimiter: new BundleUnlockRateLimiter(TimeProvider.System, BundleUnlockRateLimiter.DefaultWindow),
            options: iOpts,
            timeProvider: TimeProvider.System,
            templateRepo: Substitute.For<ITemplateEngineRepository>(),
            externalRepo: Substitute.For<IExternalSystemRepository>(),
            notificationRepo: Substitute.For<INotificationRepository>(),
            inboundApiRepo: Substitute.For<IInboundApiRepository>(),
            siteRepo: Substitute.For<ISiteRepository>(),
            auditService: Substitute.For<IAuditService>(),
            correlationContext: Substitute.For<IAuditCorrelationContext>(),
            dbContext: new ScadaBridgeDbContext(new DbContextOptionsBuilder<ScadaBridgeDbContext>().Options),
            semanticValidator: new SemanticValidator(),
            signer: BundleSignerTests.Signer(opts));
    }

    private static byte[] ReplaceEntry(byte[] bundle, string entryName, Func<byte[], byte[]> rewrite)
    {
        using var output = new MemoryStream();
        using (var src = new ZipArchive(new MemoryStream(bundle), ZipArchiveMode.Read))
        using (var dst = new ZipArchive(output, ZipArchiveMode.Create, leaveOpen: true))
        {
            foreach (var entry in src.Entries)
            {
                using var es = entry.Open();
                using var buf = new MemoryStream();
                es.CopyTo(buf);
                var bytes = entry.FullName == entryName ? rewrite(buf.ToArray()) : buf.ToArray();
                using var ds = dst.CreateEntry(entry.FullName).Open();
                ds.Write(bytes);
            }
        }
        return output.ToArray();
    }

    /// <summary>A signed bundle — plaintext or encrypted — loads as Verified on a cluster that trusts the key.</summary>
    [Theory]
    [InlineData(null)]
    [InlineData(Passphrase)]
    public async Task Signed_bundle_loads_as_Verified(string? passphrase)
    {
        var (priv, pub, keyId) = BundleSignerTests.NewKeyPair();
        var bundle = Pack(BundleSignerTests.SigningOptions(priv), passphrase);
        var importer = Importer(BundleSignerTests.SigningOptions(null, require: true, trusted: ("dev-cluster", pub)));

        var session = await importer.LoadAsync(new MemoryStream(bundle), passphrase);

        Assert.Equal(BundleSignatureStatus.Verified, session.SignatureStatus);
        Assert.Equal(keyId, session.SignerKeyId);
        Assert.Equal("dev-cluster", session.SignerName);
        Assert.Equal("Pump", Assert.Single(BundleImporter.ReadSessionContent(session).Templates).Name);
    }

    /// <summary>
    /// Re-labelling a signed bundle's manifest (here, its source environment) — which the
    /// content hash alone cannot catch for a plaintext bundle — is refused.
    /// </summary>
    [Fact]
    public async Task Altered_manifest_of_signed_bundle_is_refused()
    {
        var (priv, pub, _) = BundleSignerTests.NewKeyPair();
        var bundle = Pack(BundleSignerTests.SigningOptions(priv), passphrase: null);
        var tampered = ReplaceEntry(bundle, "manifest.json", bytes =>
            Encoding.UTF8.GetBytes(Encoding.UTF8.GetString(bytes).Replace("\"dev\"", "\"prod\"", StringComparison.Ordinal)));
        var importer = Importer(BundleSignerTests.SigningOptions(null, trusted: ("dev-cluster", pub)));

        await Assert.ThrowsAsync<BundleSignatureException>(() => importer.LoadAsync(new MemoryStream(tampered), null));
    }

    /// <summary>
    /// With signing required, an unsigned encrypted bundle is refused before the passphrase is
    /// asked for — the policy check precedes the unlock, so it spends no unlock attempt.
    /// </summary>
    [Fact]
    public async Task Required_signing_refuses_unsigned_bundle_before_passphrase()
    {
        var bundle = Pack(new TransportOptions(), Passphrase);
        var importer = Importer(BundleSignerTests.SigningOptions(null, require: true));

        await Assert.ThrowsAsync<BundleSignatureException>(() => importer.LoadAsync(new MemoryStream(bundle), null));
    }

    /// <summary>By default an unsigned bundle loads unchanged and reports Unsigned.</summary>
    [Fact]
    public async Task Default_policy_loads_unsigned_bundle()
    {
        var bundle = Pack(new TransportOptions(), Passphrase);

        var session = await Importer(new TransportOptions()).LoadAsync(new MemoryStream(bundle), Passphrase);

        Assert.Equal(BundleSignatureStatus.Unsigned, session.SignatureStatus);
        Assert.Null(session.SignerKeyId);
    }

    /// <summary>
    /// Forward compatibility: a signed, encrypted bundle is still readable through the
    /// pre-signing read path (open entries by name, AAD over the deserialised manifest) and
    /// stays inside the default zip entry-count cap — so an importer from before #45 imports it.
    /// </summary>
    [Fact]
    public void Signed_bundle_is_readable_by_pre_signing_read_path()
    {
        var (priv, _, _) = BundleSignerTests.NewKeyPair();
        var bundle = Pack(BundleSignerTests.SigningOptions(priv), Passphrase);

        using (var zip = new ZipArchive(new MemoryStream(bundle), ZipArchiveMode.Read))
        {
            Assert.Equal(3, zip.Entries.Count);
            Assert.True(zip.Entries.Count <= new TransportOptions().MaxBundleEntryCount);
            Assert.NotNull(zip.GetEntry(BundleSerializer.SignatureEntryName));
        }

        var serializer = new BundleSerializer();
        var manifest = serializer.ReadManifest(new MemoryStream(bundle));
        var raw = serializer.ReadContentBytes(new MemoryStream(bundle), manifest);
        Assert.Equal(ManifestValidationResult.Ok, new ManifestValidator().Validate(manifest, raw));
        var content = serializer.UnpackContent(raw, manifest, Passphrase, new BundleSecretEncryptor());
        Assert.Equal("Pump", Assert.Single(content.Templates).Name);

        // The manifest JSON itself carries no signature field — nothing a pre-signing
        // deserialiser or the AES-GCM associated data could trip on.
        using var doc = JsonDocument.Parse(serializer.ReadManifestBytes(new MemoryStream(bundle)));
        Assert.DoesNotContain(doc.RootElement.EnumerateObject(), p => p.Name.Contains("Sign", StringComparison.OrdinalIgnoreCase));
    }
}